TAIPEI (Taiwan News) – Investigators raided several departments of the Keelung City Government as well as the Keelung City Council Tuesday, while taking at least five officials in for questioning.

Staff told reporters that people wearing jackets identifying them as representatives of the Keelung District Prosecutors Office showed up at the city government’s departments of economic affairs and urban development at 9 a.m.

They searched offices and left taking boxes full of files and documents with them, reports said. During the evening, media reports said that in the afternoon, investigators also visited the city council to look into allegations of corruption. The search also included the office of Council Speaker Huang Ching-tai, the ruling Kuomintang’s candidate for mayor in the November 29 elections, Next TV reported.

Since the investigation was still continuing, prosecutors refused to reveal details about the case they were looking into. According to media reports, four city officials were taken in for questioning related to construction and demolition practices. One of the theories mentioned by the media was that bribes might have been paid to officials to avert the demolition of illegal structures. In particular, one model home erected on a plot of government land had been allowed to stand unaffected for a long time, reports said.

Prosecutors said they would only reveal more details about the case once the raids and searches had been completed. Interrogations of suspects and witnesses were expected to last into the night.

The raids happened as Mayor Chang Tong-rong was chairing a regular city affairs meeting, reports said. While staff informed their superiors about the investigation, the meeting reportedly went on as planned.

Chang, a member of the KMT, has met with controversy before. Last month, the Taiwan High Court annulled the suspension for five years of a 20-month prison sentence he received for forcing local police to release a woman detained for drunk driving and for slapping a police agent.

The incident caused an uproar and led to allegations that the mayor abused his power to favor acquaintances over police.

Chang was not allegedly involved in the case being investigated Tuesday. Having served two terms, he is not allowed to run for re-election in the November 29 local and regional elections.